This invention relates in general to flexure mounts for rotating members. More specifically it relates to a highly simplified flexure mount for a dynamically tuned gyroscope which provides excellent performance characteristics while being fabricated by simplified techniques.
In dynamically tuned gyroscopes it is necessary to provide a coupling between a driving shaft and a driven rotating member, typically a rotor, allowing two degrees of freedom for the rotor perpendicular to the spin axis of the shaft.
Such a coupling must satisfy a number of criteria. First, it must efficiently transfer rotational torque from the shaft to the rotor while at the same time securing the rotor in a generally predetermined location both axially and radially with respect to the shaft. Second, it must be elastic torsionally about any axis in a plane of rotation perpendicular to the spin axis. The coupling assembly must also provide an anti-spring effect which compensates for the spring coupling in the plane of rotation when the gyro is operating at its resonant speed. The coupling should also be substantially frictionless and isoelastic, that is, it should exhibit substantially uniform elasticity in any torsional direction perpendicular to the spin axis. It is also highly desirable to be able to calculate accurately the axial, radial and torsional stiffness of the suspension to design a suspension with the required isoelastic conditions.
U.S. Pat. Nos. 3,452,608 and 3,512,419 to Stiles and U.S. Pat. No. 3,702,568 to Howe describe several arrangements for achieving the aforementioned objectives. The Stiles '419 patent describes a "flexure hinge" which utilizes four arms each having a generally V-shaped cross-section. The outer ends of two of the arms are secured to mating mounting blocks fixed on the drive shaft. The outer ends of the two other arms are secured to mating blocks fixed on a rotor. In the '608 mounting system a central connecting ring secures four radially extending "hinges" each having a tubular configuration. One diametrically opposed pair of these hinges is secured to a rotor and the remaining hinges are secured to mounting brackets formed on the end of a drive shaft. The tubular hinges include a localized slot which enhances their flexure in the plane of rotation perpendicular to the spin axis.
The Howe suspension includes a generally flat "disk". It has a central portion secured to a "hub", intermediate "lands" secured to a gimbal ring, and an outer "annulus" secured to an "outermost" rotor ring or a rotor. A set of flat "spokes" connect the central portion of the disk to the outer annulus. Four other "spokes" connect the land portions to either the outer annulus or the central portion. Diametrically opposite pairs of these spokes connect the gimbal ring to the outer ring and the other two spokes connect the gimbal ring to the central hub. These latter four spokes are twisted so that the plane of each spoke is generally aligned with the spin axis. The hub, gimbal ring and outermost ring are formed in upper and lower halves. These components have suitable clearances and supporting slots machined in their facing surfaces which abut or are adjacent to the disk. The drive shaft is secured in a hole formed in the hub and the hub portion of the disk.
While the foregoing suspensions provide a universal coupling suitable for use in a dynamically tuned gyroscope, they each have deficiencies which limit their usefulness. For example, it is not simple to accurately align components of the gyroscope with the suspension system during assembly and manufacturing operations. In general, these prior art suspensions require relatively complex and costly jigs to align the component parts of the assembly and maintain that alignment during operations such as brazing or machining. The jig fixtures also typically include arrangements for controlling the placement and/or flow of brazing material to secure the parts to one another. Also, the performance of these systems is not optimal. In particular with respect to the tubular style hinges, it is difficult in practice to obtain a truly iso-elastic mount since the wall thickness and flexural qualities of the tubing are not readily maintained to extremely close tolerances. The Howe system, on the other hand, requires accurate and costly machining of what are typically very small components.
It is therefore a principal object of this invention to provide a flexure mount for a dynamically tuned gyroscope or the like which provides both the excellent performance characteristics usually associated with a highly machined one piece suspension while at the same time having a low cost of manufacture.
Another object of the invention is to provide a flexure mount which is formed from only three basic elements, two of which can be identical and each of which can be formed from a sheet material and have a comparatively simple configuration.
Yet another object of the invention is to provide a flexure mount and a method of assembly for the mount which is to a large extent self-aligning.
Another object is to provide a flexure mount whose flexure characteristics can be comparatively easily calculated to facilitate design changes.
Yet another object of the invention is to provide a flexural mount which is assembled through simultaneous multiple brazings.
A further object of the invention is to provide a flexural mount that accepts inner and outer rings fabricated by straightforward machining operations.